Method of preparing lubricants



E. H. LESLIE METHOD OF PREPARING LUBRICANTS May 31, 1932.

Filed March 7, 1928 5 Sheets-Sheet Elvwwnboz Zugene h [es/A3.

Ju flbtome c4 0 [1932- E. H. LESLIE 1,860,838

METHOD OF PREPARING LUBRICANTS Filed March 7, 1928 3 Sheets-Sheet 5i222; z z V 95 H 1 j 103 1 0 42 1:111:11: 111112 fixowhq-nmmig 7Svwemtoz [Page/we H [es/[e 851 a-ttozmm d Patented May 31, 1932 UNITEDSTATES rArsN-rerr-Ice Imam n. LEsLm, or ANN Anson, u'rcnrem, nssrenonzro E. '3. Banana &. sons com-m, or nos'ron, mssacnusnr'r s, ACORPORATION OF mssAcHUsEr'rs METHOD or Panama LUBRICANTS Applicationfiled Mar ch 7, -1e2s. sefiaimasasst My invention relates to amethod'ffor economically securing a high yield of lubricants from apetroleum or like material.

. Many crude petroleum materials from 5 which lubricants are derivedcontain a considerable amount of tarry oras haltic ma terials, which areeither ractlcally nonvolatile or have boiling polnts higher than thoseof the highest boiling lubricants.

10 These tarry or asphaltic materials must not,

bedpresent in the finished lubricants and in or er to remove them bdistillation the temperature must be sufliclently high to distill andseparate from them the desired lubriis cants. The lubricants of the hihest viscosity which in many instances are tie most valuable, are'thosehavin the highest boiling points, and it is there ore desirable to use amaximum distillation temperature and at so the same time to avoidsubstantial cracking. It is well known that the rate of cracking is afunction of temperature, the amount of cracking being generally directlypropor tional to the time and increasing rapidly with increase intemperature. Extended researches have been made by others to determinethe time and temperature factors contributing to a maximum amount ofcracking, as this information has been of great 80 importance to thetremendous industry of producing gasoline by cracking. Iam concerned onthe other hand with obtaining a minimum of cracking of the lubricatingportions of a material from which lubricants are 85 derived, in order toprevent loss of the lubricants, and at the same time with utilizingtemperatures that will permit distilling a maximum of lubricants in aneconomical manner. The precise influence of the fac- 40 tors of time andtemperature on the loss of.

lubricants by cracking has not been previously determined, and themethod of this invention is based on careful investigation andexperimental work in this field.

In the ordinary present day commercial oin' crude petroleum arelowbecause of plant procedures that destroy the viscous oil ythermaldecomposition or cracking. Us ually one or more distillations from largeshell stills are employed, and the petroleum is heated to a'relativelyhigh temperature for a period of many hours, thereby causing 1 "crackingin the bed of the .oil. Moreover, the temperature of t e oil close tothe heating surfaces is necessarily materially higher than that of thebody of the oil, and hence considerable cracking takes place in therelativel quiescent film next to the heating suraces. Endeavors havebeen made to reduce the decomposition'of the lubricants by reducing thetemperature or time of distillation or both. One process employs shellstills and lowers the temperature required by distilling under a lowabsolute pressure. The long time of heating and the'film overheatingefl'ect referred to above, are necessary consequencesof the use of shellstills, hence it follows that it is essential, if any substantialcracking is to be avoided, to maintain a very low absolute pressure,thereby permitting the use of a relatively low temperature. The

use of shell stills under such very low absolute pressures involvesrelatively high initial installation costs and operating ex penses.Another expedient in common use is to distill in shell stills and toinject steam into the oil. The effect of the steam is to lower thedistillation temperature in accord- I ance with well known principles.In addition to the disadvantages of a long time of heating andoverheating of the oil next to the heating surfaces, suchpracticeinvolves ,a.

through tubes heated externally, the time of prractice, the yields oflubricants obtainedheating and therefore the amount of cracking bem lessfor any given temperature than in s ell stills at the same temperature.

In all such heaters, however, so far as I am aware, the viscous materialor lubricant has been subjected to a time of heating such thatsubstantial cracking of lubricants results when raising the temperatureto a point where the desired amount of lubricant will be distilled. Insome cases steam has been introduced into the heating tubes to lower thedistillation temperatures, and to increase velocity, thus decreasing thetime element. In one installation a tubular type of heater has beenemployed in which the tubes are not filled with the material beingdistilled and provision is made for the removal of vapor as formed.

In contrast to present practice, my procedure is designed to securelarger yields of lubricants economically from material containing thesame by distillation in such man ner as to prevent any substantialamount of cracking. By my process, average distillation temperatureshigher than those that have previously been considered possible may beemployed without diminishing the yield of lubricants or impairing theirviscosity.

According to my invention, I heat the lubricant containing material in atubular heater to the temperature required to vaporize the desiredlubricating fractions, which temperature is normally considerably abovethe cracking temperature of 'the material, in such a manner that theperiod of time during which the material is subjected to temperaturesabove its crackin temperature is too short to permit any su stantialcracking to take place, and that the oil next to the heating surface isnot heated to a temperature considerably exceeding that of the body ofthe oil. After heating the material to the required temperature Isubject it to flash vaporization in a suitable vaporizer or flashchamber. I have demonstrated by complete experimental work theadvantages of flash vaporization as *compared with incremental orstepwise vaporization. By means of flash vaporization approximately 30%more Inbricants can be vaporized by heating to any given temperaturethan by stepwise vaporization, or the same percentage can be vaporizedby heating to a lower temperature. Furthermore,-at agiven temperaturethe desired lubricants will be more sharply separated from the viscousbottom by flash vaporization than by stepwise vaporization. To reducethe temperature required to vaporize a large part or substantially allof the ris- 'cous oils I preferably operate under a vacuum as describedmore fully hereinafter. After separating the desired lubricants from theh avy residues by flash vaporization, I prefe ably employ countercurrent fractionation in a suitable plate column to separate the after.

vapors from the vaporizer into the desired fractions. The use of a platefractionating column is essential to secure the highest yieldsoflubricants and the advantages thus obtained will be pointed out indetail herein- My process is particularly advantageous bearing oils, andan important feature of my invention resides in the treatment of theseoils in such a manner as to secure in a single operation a maximumamount of so-called pressable wax distillate. In the commercial shellstill processes heretofore employed, the wax distillate out either doesnot contain the wax in a form suitable for pressing or is divided intotwo portions during distillation, thefirst portion to go overhead beingpressable, and the second and usually larger portion beingnon-pressable. Thecustomary procedure is to redistill the wax distillateor the non-pressable part thereof in shell stills under crackingconditions, whereby a secondary wax distillate, which is pressable, ispro duced. Obviously, however, this procedure is wasteful of heat and.destroys some of the valuable lubricants. According to my invention, onthe other hand, as will appear from the detailed description givenhereinafter, a larger yield of pressable wax distillate may be obtaineddirectly from the original distillation, which is carried out undersubstantially non-cracking conditions as above de' scribed.

These and such other objects and advantages of my invention as mayhereinafter appear will be best lmderstood in connection with adescription of suitable apparatus for carrying out my process, such asis illustrated diagrammatically in the accompanying drawings, which forma part of this specification and-in which;

, Figure 1 is a diagrammatic side elevation, partially in section, of acomplete plant adapted to carry out my process;

Figure 2 is a horizontal section through a tubular heating unit whichmay be used in place of the heating unit shown in Figure 1;

Figure 3 is. a central vertical section through the heating unit shownin Figure 2;

Figure 4 isa horizontal section through anotherform of heating unit; and

Figure 5 is a central vertical section through'estill anothersuitableform of heating unit.

Referring more particularly to Figure 1 of the drawings, 10 indicatesgenerally a suitable tubular heater or pipe still for bringing thelubricant containing material to the desired distillation temperature.The pipe still 10 comprises a preheating or economizer section 11 and ahigh temperature or radiant heat section 12. The radiant heat section 12is preferably constructed in the form of an upright cylinder and isprovided at its upper P economizer section 11. From the economizerarranged circumferentially'around a portion heat section 12. In otherwords, for a typical 5 relatively slowly in the preheating or econoendwith a centrally locatedoil burner 13. The-hot products of combustlonfrom the burner 13 pass downwardly through the center of thera'diantheat section 12 and thence through the flue 14 to the economizer section11 and out through the stack 15. In the embodiment'shownin this figure,the oilto be heatedjis divided into a plurality of independent streams,four of such streams being illustrated. The oil is picked up from eachof the four supply pipes16, connected to a source of supply not, shown,by a separate pump 17, and forced through a heating c011 '18 in theeeonomizer section 11. The four independent heating coils 18 arehorizontally disposed in direct contact with the products of combustion.If desired, the oil maybe preheated in'suitableheat exchan ers (notillustrated) before being introduce into the section, each of the fourstreams of oil is separately conducted through aline 19 to the radiant.heat section 12, where it passes through a vertically disposed heatingcoil 20 of the inner Wall of the radiant heat section. The four coils 20taken together form'a hollow vertical cylinder. By this construction,

the hot produetsof combustion from the burner 13 pass centrally downwardthrough the radiant heat section, and transmit their heat thereto mainlyby radiation.. The products of combustion are. cooled materially beforethey come into direct contact with the heating coils located in the'economizer section 11-, thus preventingthe burning or'oxidation of theheating tubes. The ends of the four coils 20 in the radiant heat section12 are all connected to the common outlet header 21 disposed above theradiant heat section.-

1 preferably design'and operate the pipe still 10 in such manner thatthe oil undergoing treatment does not reach a cracking temperature untilafter it enters the radiant lubricant containing petroleum oil themaximum temperature reached inthe eeonomizer. section 11 will be, in,the neighborhood of 600 F. It is thus feasible to heat the oil mizersection. Therefore, I employ relatively large heating tubes in theeconomiz er section 11, thereby securing a cheaper andmo're dur its .the heating depends upon the character of the 105 I have found thatlwhena distillationtemapproximately 650 F., to the maximum temture is lower,and vice versa; However, in.

exist in the portion of the tubes near the outlet header 21.

mum temperature which must be obtained depends of course upon thecharacterof the material and the percentage thereof which it is desiredto vaporize. The first requirement in the design of the heater obviouslyis that the area of the heating surface must be large 9 enough so thatthe amount of heat required to raise the oil to the desired distillationtemperature can be put into the oil.

The maximum time during which the mate'- rial is above its crackingtemperature may be determined by dividing the material capacity oftheportion of the'heater in which the material is aboi e its crackingtemperature, in this case the radiant heat section 12, by the amount ofsaid material which passes through this portion of the heater in a unitof time.- For instance, if the material capacity of the radiant heatsection 12 should be thirty gallons and the material put through onegallon per second, it would require a maximum of thirty seconds for thematerial to pass through this portion of the pipe still. 7 Throughoutthis specification I have defined the time during which the material isheld at 'I a temperature above its cracking temperature in this manner,disregarding such variations as may result'from' theformation of gas orvapor.

The permissible time for this final stage of material undergoingtreatment and the maximum temperature to which it is -to be heated.

perature of about 850 F. is desired, it is possible to avoid substantialcracking if the oil is raised from its cracking temperature, or

perature in about 60 seconds. A longer time is permissible if thedistillation temperaorder to secure the best results, I prefer not toheat the oil at temperatures above its crackingtemperature for more than35 seconds.

, have further found that the velocityat which the material passesthrough the heat- 12 ing tubes is of great importance, and that thisvelocity must be high. In order to prevent any substantial cracking ofthe oil being heated, it is necessary that no portion of the oil streambe materially higher in temperature than the main body of the oil. Thevelocity of flow determines to a large extent the temperature gradientbetween the oil v close to the tube walls and that at the center 13 ofthe tubes. A high velocity of flow apparently sets up a turbulentcondition which aids in preventing any great differences of temperaturein the oil stream.

There are thus three major factors which I consider in the design of thetubular heater:

First, the area of the heating surface must be great enough-so that therequired amount of heat can be put into the oil; second, the ma terialcapacity of the heating tubes must be sufiiciently small so that thetime of passage of the oil will be 60 seconds or less; and, third, thevelocity of the oil through the tubes must be such that high filmtemperatures on the tube walls are avoided. At the same time, care mustbe taken that the velocities and tube lengths used are not such as wouldgive an excessively high pressure drop through the heater.

As a result of my experimental work, I have found that for commercialsize plants,

--tub es of 1% inside diameter or less are desirable, and thatvelocities of 10 feet per second or over must be used. For large unitsin which a single tube of the required area would be so long that thepressure drop would be excessive, I may use several tubes in parallel.

The oil after being heated to the required final temperature isdischarged into the flash vaporizer 30, which may be, as shown in Fig--ure 1, interposed in the periphery of the outlet header 21. The materialentering the vaporizer 30is above its boiling point at the pressureexisting therein, and a substantial portion of the material willtherefore immediately. flash into vapor, which leaves the vaporizerthrough the overhead pipe 31.

One or more baffle plates 32, which may be of I viscous lubricants.

the usual bubble tower type, are, if desired, placed in the top of thevaporizing chamber 30 to prevent entrainment of liquid in the vaporsleaving the chamber. I have illustrated the flash vaporizer 30 onlydiagrammatically as any suitable type thereof may be employed.

The liquid residue remaining in the vaporizer 30 may be drawnofl throughthe valve 33 into a cooling coil 34, which discharges into a receivingtank 35 provided with a drawofl pipe 36.

The vapor leavmg the vaporizer through the pipe 31 mayv be led to asuitable fractionating column 40 where the lubricating stock may be cutinto fractions of desired viscosity and, if. desired, the lighternonviscous material may be stripped from the The column 40 is providedwith a series of plates 41 which may be of the usual bubble tower type.The heavy lubricant collecting in the bottom of the fractionating columnd 40 may be drawn off through the pipe 42 controlled by the valve 43into a cooling coil 44. The cooling coil 44 discharges into a receivingtank 45 provided with a drawoif 46.

' drawofl'pipe 40 which is connected to a cooling coil 51 discharginginto a receiving tank] 52. It will be understood that more thanoneintermediate drawofl. such as may be provided if desired.

The overhead vapors from the fractionating column 40 are conductedthrough the pipe to a condenser 61. The condenser 61' discharges into atrap 62 from which the condensate is conducted through a pipe 63 to 'acooler 64, discharging into a receiving tank 65. The vapor space of thetrap 62 is connected bythe pipe 66 to a vacuum pump 67, v

by means .of which the desired low absolute pressure may be maintainedin the-vaporizingsystem.

The receiver is provided with a valve controlled drawofl pipe 70 andalso wlth a valve controlled pipe 71 leading to a ump 7 2, which pumpsthe desired quantity 0 con-' densate through the line 73into the top ofthe fractionating column 40 to provide the necessaryreflux to secure theproper operation of the fractionating column. The valve 74 may be usedto control the amount of reflux introduced into the column.

The manner of carrying out the'flash vaporization and the countercurrent fractionation steps of my method depends, to a considerableextent, upon the character of the oil being treated. A broad line ofdivision may be made between the handling of non-waxbearing oils and ofoils containing wax, and the latter classification may be sub-dividedagain into those of mixed base and'thoseof parafiin base.

In the treatment of non-wax-bearing oils, a-temperature in the vaporizer30 is prefer ably maintained such that the residue remain ing thereinand drawn ofi through the valve 33 forms. but a small proportionofthe'stock charged, and consists largely of tarry, vasphaltic, gummy,andcoloring substances.

The viscous stocks vaporized overhead and recovered in the bottom of thefractionating column 40 are oils of good color as well as of highviscosity and may be sold as cylinder stock without filtration and withvery little refining treatment. In previous processes in which cylinderstocks have been made from various oils, on the contrary, these stocksor the most viscous lubricants remain as a still residue, and filtrationor a heavy treatment with sulphuric acid, or both, are usuallynecessary,particularly in the production of bright stocks from mixedbase oils such as Mid-Continent oils.

Non-wax-bearing oils may be cut in the fractionating column 40' directlyinto frac- Isa tions of the desired viscosity. Thus, for ex-- am ssthrough the pipe 50, and a heavirlubricant from the bottom of the columnt ough the pipe 42. If the chargin stock contains only enough gas oil orother hght fractions to obtain an overhead roduct of the desiredviscosity, a light lu ricating materialmay be taken overhead from thecolumn 40 and collected in the receiving tank 65.

Most present day commercial methods of lubricatm oil manufacture are, Ibelieve,

based on t e method of simple distillation or difierential vaporizationwith little or no fractionation of the vapor so formed. Most stills-haveno fractionating devices or even partial condensers. In actual practice,the

lubricating oil in the" still may contain considerable gas-oil. Thepresence'of this gas oil lowers the viscosity of the lubricating oil,

p not only in proportionrto the concentration 2 of the gas oil butconsiderably more because viscosities are not additive. In other words,blending equal parts of two oils, one of 200 ;,viscosity and the otherof 100 viscosity will j give a blendnot of 150viscosity'but ofconsiderably less. In the reduction of petroleum oils torequiredviscosity by simple distillation in a shell still, the distillationmust-be carried to such a point that the gas oil con centration in thestill is .low,-,which results,

86 therefore, in a large loss of valuable lubrieating oil in the gas oilvapors normally passed overhead. Byemploying'a'fractionating columnaccording to my invention, on the other hand, I can cleanly strip thelubricating stock from inclusions of non-viscous lighter oils which maybeseparated overhead without loss ofvaluable lubricants, and can sharplyseparate heavy viscous lubricants from those of lower viscosity. 46 Inthe manufacture of lubricants from wax-bearing oils it is, of course,essential to separate the wax from the -lubricatingoil in some manner,The wax present in pe- 8 troleum oils maybe classified accordingto 4talline waxnot in pressable form, and (a) In this classificationamorphous wax is wax the crystal growth of which has been practicallycompletely prevented by inhibiting substances. 7 These substances areheat sensitive and can be destroyed by cracking; They are highboiling-and can be removed from the lower boiling lubricating fractionsby counter, current fractionatiom As an example of amorphous wax it'maybe noted that thewell:

known petrolatum of commerce containsa large part of itswax in theamorphous oi' ncmcrystalline state. By crystalline wax not in pressableform is meant wax the crystal growth of which has been partiallyinhibited, that is, to suchan extent that the crystals cannot easily 'beremoved by filtratidn in a filter press. Amorphous wax and crystallinewax not in pressable form are reits state, as: (a) amorphous'wax,"(b)erysferredto collectively in this specification as non-pressable wax.Pressable wax, as the term isused herein, is wax in the form of crystalsthat deposit on the press cloth and on the frame of the press to form areason- ,ably open crystal mass through the interstices of which oil canflow.

In handling wax-bearing lubricatin oils the usual shell still practiceis to disti ofi successively ,the gasoline, kerosene and gas oil andthen to take overhead a so-called wax distillate, the difierentfractions being conducted to separate receiving tanks. The distillationis usually conducted at atmospheric pressure, steam being employedduring the later stages -to avoid excessive cracking. The wax distillateis ordinarily collected as a single fraction, but in some cases it isdivided into two cuts, thevfirst cut to 0 overhead being usually muchsmaller t an the second. Where a'single wax distillate cut is made,-itis not pressable in the-form in which it isoriginally obtained, andthesame is true of thesecond out where two outs of wax distillate aremade.- This non-pressable wax distillate must be redistilled to secure apressable wax distillate. In redistilling this'wax distillate, whichoperation like the original distillation is usually carried out atatmospheric pressure, the heat treatment is intentionally made such thatconsiderable cracking takes place; The substances inhib iting waxcrystal growth areheat sensitive and aredestroyed to such an extent thatwax crystals of reasonable size will grow in the 10o so-called crystalliwax-distillate taken overhead from the crystallizing still. Thiscrackingoperation has heretofore always been considered essential to convert thewax in the wax distillate into pressable form. The redistilled waxdistillate contains the wax in pressable form and the still residues.remaining from'this second distillation is commonly-sold as a cheaplubricant or black oil. The wax is removed from the pressable no waxdistillate by filtering throu h a filter press and the resulting pressedistillate is then redistilled into cuts of suitable viscosi-- ties orboiling points. It will be understood that the wax distillate containssufiicient gas. "5

" the presence of these wax crystallization inhibitors that renders theoriginal wax distillate in the usual'shell still operation nonpressable.I have "further discovered that these wax, crystallization inhibitorsare high boiling substances that can be separated from the waxdistillate by counter current'fractionation, thus making it possible toobtain directly a pressable wax distillate without the step ofredistilling and cracking. For

example, traces of high boiling, resinous,

tarry or asphaltic substances in the wax distillate may act as waxcrystallization 1nh1b- .itors and prevent obtaining the crystallizablewax in pressable form.- These high boiling substances appear tointerfere with the growth ofthe wax crystals by retarding the movementof the crystallizable wax molecules in the solution and by coating thewax crystal nuclei. Moreover, these same inhibiting substances or otherhigh boiling substances in the oil increase the solubility of wax in oiland oil in wax, thus interfering with the separation and proper growthof wax crystals.

According to my invention wax crystallization inhibitors are partiallyleft in the residue of the vaporizer. The vapors leaving the vaporizerare subjected to counter current fractionation in the fractionatingcolumn as described and the high boiling, resinous, tarry and asphalticsubstances are removed from the wax distillate containing thecrystallizable wax thus obtaining a maximum yield of pressable waxdistillate in a single operation. It will be apparent that bymy processI avoid the destruction of valuable lubricants by cracking and alsoavoid the heat loss incident to a second distilling operation.Furthermore, I am enabled to get a sharper separation between thecrystallizable wax and the amorphous wax than is possible in priorprocesses. This permits me in the rimar distillation to obtain a largerpart 0 the orl as directly pressable wax distillate than is ordinarilyobtained as pressable distillate after the primary and crystallizingdistillations. Since pressing is a less expensive operation. than eitherof the other well known methods of wax removal, namely, cold set tlingand centrifuging, it is, of course, desirable to secure as large aproportion of the oil as is possible in the form of pressable waxdistillate.

It will be seen that my process possesses three major advantages overthe prior art processes in the treatment of wax-bearingoils, first,substantially no cracking takes place during the original distillationof the oil; second, the necessity of redistilling and cracking toproduce a pressable wax distillate is eliminated; and third, a cleanseparation among the various cuts may be ob-- tained. Each of theseadvantages assists in obtaining a final maximum yield of valuablelubricants.

When a mixed base oil containing wax is being treated, the vaporizerresidue will be relatively small as described in connection with thetreatment of non-wax-bearing oils, and will contain the asphalt and alarge part of the tarry wax crystallization inhibitors The fractionatingco umn bottoms will com prise a heavy lubricant containing the highboiling, non-pressable waxes, but the larger proportion o the waxpresent in the crude will be contained in the light fraction drawn oflfthrough the pipe 50. This fraction is amorphous wax or mineral jellyreferred to above, and in addition will contain some of the higherboiling paraflins which may be pressed only with great difliculty. Theheavy lubricant drawn from the bottom of the fractionating column may besubjected to refining treatment only, or may be subjected to colsettling or centrifuging followed by refining treatment. In some cases,it is advisable to combine the heavy stocks collected in the tanks 35and 45 and subject the mixture to a cold settlin or centrifuging toremove the wax, and, i desirepili to subsequent'refining treatment suchas tering.

During all of the operations above described, I- preferably maintain anabsolute pressure of about 25 mm. in the vaporizer 30 y operation of thevacuum pum 67. The absolute pressure at the pump itse f will usually beappreciably less than the ressure in the vaporizer, the pressure dro troughthe fractionating column 40 and t e connecting piping beingresponsible for the difference. It will be apparent that the pressuresat the pump and inthe fractionating column are-absolutely immaterialexcept in so far as they determine the pressure in the va orizer. Inorder words, the function of the ow absolute pressure in the vaporizeris to enable the vaporization of the required percentage of the chargingstock at a lower temperaturethan would otherwise be necessary and oncethis object is accomplished and the vaporshave dropped below theircracking tempera ture, the pressure under which the subsequentstartingmaterial for my process a. reducedcruderather than a crude containingthe This is adnatural gasoline and kerosene. visable in order to reducethe burden upon the lac apparatus and to make the operation moreeconomical.

The foregoing operations have been sucillustrative runs made inaccordance with I this invention on two of the three types of chargingstock above discussed:

I Asphaltz'c base permeate-bearing oil Charging stock, Orange CountyGulf Coast reduced crude (70% bottoms).

Charging rate, 50 gallons per hour.

Products g Viscosity Totalvaporized 88. 1 Light overhead out... 34. 6Medium out. 34.2 60 sec. 210 F. Heavy viscous cut 19. 3 161 sec. 210 Tarbottoms 11. 7

Temperatures Outlet of heater 845-860 F. Vapor from vaporizer 719731 F.Vapor (mm column 390 F.

Pressures (absolute) Top of column-.. mm. Vaporizer. 1 r 31-32 mm.Velocity of oil in heater 1.79 ft./sec. Total time of oil in heater 112seconds Probable time in heater at temperature above 650 F 60 secondsII. M iced base wee-bearing oz'l Charging stock, mixture of Powell andPrairie Pipe Line Midcontinent reduced crudes (47% bottoms).

Gravity, 245 A. P. I.

Charging rate, 61.5 gallons per hour.

Products m Viscosity Total vaporized 82. 5 I

Wax distillate 63. 2 29. 3 79. 5 sec. 100 F. Heavy viscous cut 19. 3.138 sec. 210 F. Tar bottoms 17. 5 I

Temperatures 5 Outlet 01 heater 826 F.

Vapor from vaporizer 724 728 F. Vapor from column 530 F.

Pressures (absolute) Top of column 20 mm.

a rizer 36-38 mm. 50 Ve ocity of oil in heater 2.20 ttJsec. "Total timeof oil in heater" 91 seconds Probable time in heater at temperatureabove 650 Ft. 50 seconds It will be understood that the pressures,temperatures and other data given in these runs are not in any senselimiting values, but are simply illustrative of suitable values for theparticular charging stocks. In computing the velocity of the oil in theheater and the timewhich the oil is in the heater, it was assumed,first, that the oil remainsin the liquid phase throughout its passagethrough the heater, and second, that the average density of the oil isits density at 500 F.

In each of these runs the distillation was effected without anysubstantial cracking taking place even though the final temperature Thefollowing are lar heater. .It will be noted that the lowest at theoutlet of the heater was well above the 1cracking temperature of thecharging. stoc t. plished without the use-of steam in the tubu-Moreover, this result was accom--- absolute pressure used in thevaporizer in either of these runs was 31 mm., but I have found itadvisable in some instances to uti-- lize considerably lower pressuresin the vaporizer. Ordinarily, however, I maintain an absolute pressurein the vaporizer in the neighborhood oft25 mm. of mercury.

At first glance the velocity of the oil in the neighborhood of two feeter second, appears to be far outside the pre erred range of veter of0.49. With pipe of this internalj diameter, a velocityof about two feetper secs end is sufiicient to avoid any injurious skin effect and tosecure a turbulent flow. The velocity of ten feet per second referred toabove is applicable to tubes'of the ordinary sizes used in commercialpipe stills. In this connection it may be stated here that the velocityof ten feet per second is higher than that ordinarily used' in such pipestills.

heater in the foregoing runs, which'is in the Knowing the velocityrequired with one size of pipewhenheating a given oil to a specifiedmaximum temperature to obtain a suitable temperature gradient betweenthe oil at the outside of the pi e'and that at the center, that is tosay, t e velocity required. to. I

avoid injurlo'us skin efiect, it is possible to compute by well knownformulae the velocity which must be maintained to obtain the sametemperature gradient when using a pipe still having pipes ofa differentsize. In other words, the relationship between velocity and temperaturegradient has been already drawings, these figures disclose a modifiedform of pipe still which may be advantageously employed in carrying outmy process. The furnace 80 is provided with a burner 81 arranged at oneend' of the furnace near the floor thereof and discharging into a rediant heat or combustion chamber 82. The products of combustion areforced to pass upwardly over a bridge wall 83, down through a convectionheat chamber 84 and thence u wardly through a stack 85. A dependingaflie 86 is arranged in front of the bridge wall 83, forming apassageway 87 between the bridge Wall and the baflle throughpreferablyso designed that the oil does. not

reach a cracking temperature until it enters the coils 90.

It will be understood that in carrying out the process of my invention,the pipe still 80 is simply-substituted for. the pipe still 10 in theplant shown in Figure. 1. The pipe still 80 has the advantage of beingcons'iderably simpler in construction than the pipe still 10 andinay beused whenever it is not necessary to divide the oil t6 be heated into aplurality of streams as shown in Fig- "ure 1.

Figure 4 shows still. another form of pipe still in which the oil ispassed through t e convection heat section in a single stream and isthen split into a plurality of streams be fore passing through theradiant heat section in which it reaches a cracking temperature. In thisfigure, 95 represents the pipe still as a whole, and the constructionaldetails of the furnace may be exactlythe same as those shown in Figures2 and 3 except for the arrangement of the heating tubes.

The same reference characters are therefore used for similar parts. Inthe furnace illustrated in Figure 4, the oil to be heated is introducedinto the heating coils 89 located in the convection heat chamber 84 andpasses thence into a manifold 96 from which the oil is delivered to theradiant heat or high temperature section of the furnace. A plurality ofhigh temperature heating coil-s 97, in this instance four, are locatedalong the roof of the combustion chamber 82, and have their inlet endsconnected to the manifold 96 and their outlet ends to a manifold 98. Avalve 99 is located at the inlet endof each (if the coils 97 to regulatethe. quantity of oil flowing therethrough. If desired, a separate pumpmay be placed at the inlet of each of the coils 97 to pick up thepreheated oil from the manifold 96 and force it through'the. hightemperature coils. I

In the pipestill 105 shown in Figure 5, a

burner 106 is located in a small combustion.

chamber 107 anterior to the main radiant heat chamber 82. The heatingtubes 89 located in the convection heat chamber 84 discharge into aradiant heat coil 108 located along the roof of the chamber 82. The coil108, is formed of tubes of smaller diameter than those in' the coil 89,and is connected to a helical coil 109 located directly in front of theburner 106 and through which: the

- products of combustion from the burner'pass.

The coil 109 is made of tubing still smaller in diameter than that ofthe coil 108. .-By this construction the oil is given a final very shortexposure to the highest temperature action, and that the rate ofcracking increases very rapidly as the temperature is raised.

WVhen, therefore, I refer to a temperature below the crackingtemperature, Iintend to define a temperature such that even though anormal time be allowed for the .reaction,

no substantial amount of cracking will occur,

and when I refer to a temperature above the cracking temperature, I meana temperature such that under such time conditions a substantial amountof cracking will occur.

VVher'e thev expression temperature gradient is employed in the claims,it is intended to mean the difference in temperature between the oilnear the surface of the tubes of the tubular heater and that at thecenter of the tubes. y

' It will be understood that my invention is not limited to the specificembodiments described and that various deviations may be made therefrom.It will be apparent also that some of the features of my invention maybe used entirely independently of the employment of other featuresherein disclosed. I desire to be limited, therefore, only by the scopeof the appended claims. I I

I. The method of preparing. lubricants from non-overhead wax-bearinglubricating oil which comprises passing the material under treatmentunder an initial pressure through a tubular heater, heating saidmaterial during its passage through said heater-to a temperature aboveits cracking temperature, the period during which the material is heatedabove its cracking temperature and the velocity of the material duringsaid period ,being such. that no substantial amount of cracking ofthematerial takes place, subjecting said material to flashvaporization'under a low absolute pressure to vaporize a substantialportion thereof and to separate certain wax crystallization inhibitorstherefrom, subjecting the resulting vapors to counter-currentfractionation, and

cutting said lubricants into arelatively light lubricating fractioncontaining wax in pressable form and-a relatively heavy lubricatingfraction containing the balance of the wax crystallization inhibitors.

2. The method of preparinglubricants from wax-bearing lubricating oilwhich comprises passing the material under treatment under aninitialpressure through a tubular heater, heating said material during itspassage, through said heater to a temperature of over 750 F., the periodduring which the material is heated above its cracking temperature beingless than 35' seconds and the velocity of the material during saidperiod being such as to produce a low temperature gradient, subjectingsaid material to flash vaporization to vaporize a substantial portionthereof and to separate certain wax crystallization inhibitorstherefrom, subjecting the resulting vapors to counter-currentfractionation, and cutting said lubricants into a relatively lightlubricating fraction containing wax in pressable form and a relativelyheavy lubricating fraction containing the balance of the waxcrystallization inhibitors.

3. The method of preparing lubricants from wax-bearing lubricating oilwhich comprises passing the material under treatment under an initialpressure in the absence of steam through a tubular heater, heating saidmaterial during its passage through said heater to a temperature of over750 F., the period during which the material is heated above itscracking temperature being less than 35 seconds and the velocity of thematerial during said period being such as to produce a low temperaturegradient, 'subjecting said material to flash vaporization under a low.absolute pressure to vaporize a substantial portion thereof and toseparate.

certain wax crystallization inhibitors therefrom, subjecting theresulting vapors to counter-current fractionation, and cutting saidlubricantsinto a relatively light lubrieating fraction containin wax inform and a relatively eavy lu ricating fraction containing the balanceof the wax crystallization inhibitors.

4. The method of preparing lubricants from non-overhead wax-bearinglubricating oil which comprises heating the oil in a con fined flowingstream to a point well above its cracking temperature for a period oftime insuificient to cause any substantial amount of cracking of the oilsubjectin said oil to flash vaporization under a low a solute pressureto vaporize a substantial portion thereof and to separate certain waxcrystallization inhibitors therefrom, subjecting the resulting vapors tocounter-current fractionation,

and cutting said lubricants into a relatively light lubricating fractioncontaining wax in {from the remaining vapors a directly pressable waxdistillate.

6. The method of preparing lubricants from non-overhead wax-bearinlubicating oil which comprises passing t e material under treatmentthrough a tubular heater, heating said material during its passagethrough said heater to a temperature above its cracking temperature, theperiod during which said material is heated above its crackingtemperature being such thatno substantial amount of cracking of thematerial takes said material during its passage place, subjecting saidmaterial to flash vaporization under a low absolute pressure to vaporizeasubstantial portion thereof, subjecting. the resulting vapors tocounter-current fractionation to separate wax crystallization inhibitorstherefrom, withdrawing the remaining vapors, and condensing the same toform a directly pressable wax distillate containing the major portion ofthe crystallizable wax initially present in the material.

In testimony whereof, I have signed my name to this specification this27th day of February, 1928.

' EUGENE H'. LESLIE.

pressable pressable form and a relativeli heavy lubrieating fractioncontaining the alance of the wax c stallization inhibltors.

. 5. 0 method of preparing lubricants

